Extracellular calcium chronically induced human osteoblasts effects: specific modulation of osteocalcin and collagen type XV

Layer-by-layer self-assembly of PLL/CPP-ACP multilayer on SLA titanium surface: Enhancing osseointegration and antibacterial activity in vitro and in vivo

Dental Implants are expected to possess both excellent osteointegration and antibacterial activity because poor osseointegration and infection are two major causes of titanium implant failure. In this study, we constructed layer-by-layer self-assembly films consisting of anionic casein phosphopeptides-amorphous calcium phosphate (CPP-ACP) and cationic poly (L-lysine) (PLL) on sandblasted and acid etched (SLA) titanium surfaces and evaluated their osseointegration and antibacterial performance in vitro and in vivo. The surface properties were examined, including microstructure, elemental composition, wettability, and Ca2+ ion release. The impact the surfaces had on the adhesion, proliferation and differentiation abilities of MC3T3-E1 cells were investigated, as well as the material's antibacterial performance after exposure to the oral microorganisms such as Porphyromonas gingivalis (P. g) and Actinobacillus actinomycetemcomitans (A. a). For the in vivo studies, SLA and Ti (PLL/CA-3.0)10 implants were inserted into the extraction socket immediately after extracting the rabbit mandibular anterior teeth with or without exposure to mixed bacteria solution (P. g & A. a). Three rabbits in each group were sacrificed to collect samples at 2, 4, and 6 weeks of post-implantation, respectively. Radiographic and histomorphometry examinations were performed to evaluate the implant osseointegration. The modified titanium surfaces were successfully prepared and appeared as a compact nano-structure with high hydrophilicity. In particular, the Ti (PLL/CA-3.0)10 surface was able to continuously release Ca2+ ions. From the in vitro and in vivo studies, the modified titanium surfaces expressed enhanced osteogenic and antibacterial properties. Hence, the PLL/CPP-ACP multilayer coating on titanium surfaces was constructed via a layer-by-layer self-assembly technology, possibly improving the biofunctionalization of Ti-based dental implants.

Screening of periodontitis-related diagnostic biomarkers based on weighted gene correlation network analysis and machine algorithms

BACKGROUND

Periodontitis is a common oral immune inflammatory disease and early detection plays an important role in its prevention and progression. However, there are no accurate biomarkers for early diagnosis.

OBJECTIVE

This study screened periodontitis-related diagnostic biomarkers based on weighted gene correlation network analysis and machine algorithms.

METHODS

Transcriptome data and sample information of periodontitis and normal samples were obtained from the Gene Expression Omnibus (GEO) database, and key genes of disease-related modules were obtained by bioinformatics. The key genes were subjected to Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and 5 machine algorithms: Logistic Regression (LR), Random Forest (RF), Gradient Boosting Decisio Tree (GBDT), Extreme Gradient Boosting (XGBoost), and Support Vector Machine (SVM). Expression and correlation analysis were performed after screening the optimal model and diagnostic biomarkers.

RESULTS

A total of 47 candidate genes were obtained, and the LR model had the best diagnostic efficiency. The COL15A1, ICAM2, SLC15A2, and PIP5K1B were diagnostic biomarkers for periodontitis, and all of which were upregulated in periodontitis samples. In addition, the high expression of periodontitis biomarkers promotes positive function with immune cells.

CONCLUSION

COL15A1, ICAM2, SLC15A2 and PIP5K1B are potential diagnostic biomarkers of periodontitis.

Mineralized collagen as a bioactive ink to support encapsulation of human adipose stem cells: A step towards the future of bone regeneration

Bioprinting - printing with incorporated living cells - has earned special attention on tissue engineering approaches, aiming to closer reproduce the 3D microenvironment of the target tissue. However, it raises extra complexity related to the need to use cell-friendly printing conditions that still comply with material printing fidelity. Inspired by the composite nano structural organization of mineralized tissues, this work reports the efficiency of the chemical approach followed to in situ mineralize blue shark skin collagen, at a nano scale level, to ultimately produce stable inks. The influence of initial cellular density was evaluated by assessing three different concentrations (2.5, 5 and 7.5 × 10⁶ cells·ml^-1) of human adipose stem cells (hASC), with the higher density of encapsulated cells presenting improved viability in a long culture term. Immunodetection of osteogenic-related markers, like RUNX2 and osteopontin, 21 days after cell culture in basal conditions confirmed the potential of the ink to be applied for osteogenic purposes, which may be associated with the success of the cell-to-ink interaction and the Ca²⁺ ions released from the co-precipitated hydroxyapatite. A combination of mineralized shark collagen, alginate and hASC is thus proposed as a bioactive bioink with potential properties for regeneration of bone tissue.

Collagen XV Promotes ER Stress-Induced Inflammation through Activating Integrin β1/FAK Signaling Pathway and M1 Macrophage Polarization in Adipose Tissue

Collagen XV (Col XV), a basement membrane (BM) component, is highly expressed in adipose tissue, and studies have found that Col XV is related to extracellular matrix (ECM) remodeling involving in adipose tissue fibrosis and inflammation. Furthermore, the ECM is essential for maintaining normal development and tissue function. In this study, we found that Col XV is related to the endoplasmic reticulum stress (ERS) and inflammation of adipose tissue. Moreover, we found that overexpression of Col XV in mice could cause macrophages to infiltrate white adipose tissue (iWAT). At the same time, the expression of the ERS sensor IRE1α (Inositol-Requiring Enzyme-1α) was significantly up-regulated, which intensified the inflammation of adipose tissue and the polarization of M1 macrophages after the overexpression of Col XV in mice. In addition, after overexpression of Col XV, the intracellular Ca²⁺ concentration was significantly increased. Using focal adhesion kinase (FAK) inhibitor PF573228, we found that PF-573228 inhibited the phosphorylation of FAK and reversed the upward trend of Col XV-induced protein expression levels of IRE1α, C/EBP-homologous protein (CHOP), and 78 kDa glucose-regulated protein (GRP78). After treatment with IRE1α inhibitor STF-083010, the results showed that the expression of adipocyte inflammation-related genes interleukin 6 (IL-6) and tumor necrosis factor α (TNFα) significantly were decreased. Our results demonstrate that Col XV induces ER-stress in adipocytes by activating the Integrinβ1/FAK pathway and disrupting the intracellular Ca²⁺ balance. At the same time, Col XV regulates the inflammation induced by ER stress in adipocytes by promoting IRE1α/XBP1 (X-Box binding protein 1) signaling. Our study provides new ideas for solving the problems of adipose tissue metabolism disorders caused by abnormal accumulation of ECM.

Mmu_circ_003795 regulates osteoblast differentiation and mineralization in MC3T3‑E1 and MDPC23 by targeting COL15A1

Circular RNAs (circRNAs) are a class of non-coding RNAs that exhibit important regulatory roles in various biological processes. However, the role of circRNAs and their potential role in osteoblast differentiation and mineralization is unclear. The aim of the present study was to investigate the expression of mmu_circ_003795 and its effect on collagen type XV α 1 chain (COL15A1). First, it was identified that the expression levels of mmu_circ_003795 and osteopontin (OPN) were upregulated in the induced cells. Silencing of mmu_circ_003795 reduced the gene and protein levels of COL15A1 and OPN, whereas the expression level of mmu-microRNA (miR)-1249-5p was upregulated. In addition, after 7 or 14 days of induction, alkaline phosphatase and Alizarin Red-S staining were decreased in the mmu_circRNA_003795 inhibitory group compared with the negative control group. In conclusion, mmu_circ_003795 may regulate osteoblast differentiation and mineralization in MC3T3-E1 and MDPC23 cells via mmu-miR-1249-5p by targeting COL15A1.

Collagen XV, a multifaceted multiplexin present across tissues and species

Type XV collagen is a non-fibrillar collagen that is associated with basement membranes and belongs to the multiplexin subset of the collagen superfamily. Collagen XV was initially studied because of its sequence homology with collagen XVIII/endostatin whose anti-angiogenic and anti-tumorigenic properties were subjects of wide interest in the past years. But during the last fifteen years, collagen XV has gained growing attention with increasing number of studies that have attributed new functions to this widely distributed collagen/proteoglycan hybrid molecule. Despite the cumulative evidence of its functional pleiotropy and its evolutionary conserved function, no review compiling the current state of the art about collagen XV is currently available. Here, we thus provide the first comprehensive view of the knowledge gathered so far on the molecular structure, tissue distribution and functions of collagen XV in development, tissue homeostasis and disease with an evolutionary perspective. We hope that our review will open new roads for promising research on collagen XV in the coming years.

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Type XV collagen belongs to the multiplexin subset of the collagen superfamily.

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It is evolutionarily conserved collagen and associated with basement membranes.

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This collagen/proteoglycan hybrid molecule contains an anti-angiogenic restin domain.

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It has important functions in the cardiovascular and the neuromuscular systems.

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Its expression is dysregulated in various diseases including cancers.

Enhanced osteogenic differentiation of osteoblasts on CaTiO3 nanotube film

Improved implant-bone interface interaction for rapid formation of strong and long-lasting bond is significantly important in orthopedic clinics. Herein, Ca-doped TiO₂ nanotube film (M-CaNTs) with enhanced adhesion strength was fabricated on titanium (Ti) surface by an anodization-hydrothermal treatment. Results showed that TiO₂ nanotube film (M-NTs) fabricated by modified anodization was amorphous, exhibiting 100-nm diameter and 12-nm tube wall thickness. After hydrothermal treatment, the nanotubular structure of M-CaNTs kept integrated, but was volume-expanded, exhibiting a decreased diameter (∼ 60 nm) and an increased wall thickness (∼ 30 nm). The formation of M-CaNTs proceeded preferentially at the interior surfaces of the closely aligned nanotubes, involving an in situ dissolution-recrystallization process. Though the adhesion strength of M-CaNTs was weakened by the volume-expansion derived internal stress, it was still higher than that of the traditionally obtained one. In the in vitro investigations, the combination of nanotubular structure and Ca²⁺ could expectedly enhance the attachment, spreading and proliferation of MC3T3-E1 cells, as well as promote the expressions of bone-specific genes, intracellular proteins and ALP activity, which in turn accelerated collagen secretion and ECM mineralization. This work provides an attractive potential for the surface modification of Ti-based implants in clinical application.

Specific concentration of hyaluronan amide derivative induces osteogenic mineralization of human mesenchymal stromal cells: Evidence of RUNX2 and COL1A1 genes modulation

Hyaluronic acid (HA) is an ideal material for tissue regeneration. The aim of this study was to investigate whether a hyaluronan amide derivative (HAD) can enhance the mineralization of human mesenchymal stem cells (hMSCs). Osteogenically induced hMSCs cultured with or without HAD at different concentrations (0.5 mg/ml or 1 mg/ml) were analyzed for mineral matrix deposition, metabolic activity, cellular proliferation, and the expression of 14 osteogenic genes. Unmodified HA (HYAL) was used as control. We demonstrated that only cells treated daily until day 28 with 0.5 mg/ml HAD, but not with 1 mg/ml of HAD and HYAL, showed a significant induction of mineralization at day 14 compared to the osteogenic control group. HAD at both concentrations tested, significantly decreased the expression of the proliferating marker MKI67 at day 2. By contrast, increased metabolic activity was induced only by HYAL from day 14. HAD at both concentrations significantly down modulated SNAI2, DLX5, RUNX2, COL1A1, and IBSP genes, while significantly up regulated COL15A1. The induction of mineralization of 0.5 mg/ml of HAD at day 14 was significantly dependent on a specific modulation of RUNX2 and COL1A1. Our data demonstrate that only 0.5 mg/ml of HAD, but not HYAL, modulated hMSCs osteogenic differentiation, suggesting that the physicochemical features and concentration of HA products could differently affect osteogenic maturation.

Immunoelectron microscopic localization of Collagen type XV during human mesenchymal stem cells mineralization

Purpose/Aim of the study. Collagen type XV (ColXV) was identified, in our previews studies, as a novel component of bone extracellular matrix. The present study aims to investigate ColXV localization during mineralization of osteodifferentiated human mesenchymal stem cells (hMSCs).

MATERIAL AND METHODS

hMSCs cultured in osteogenic medium have been analyzed at day 14 and 28 for mineral matrix deposition by alizarin red S staining, ultrastructural analysis and ColXV localization by immunogold electron microscopy.

RESULTS

Our data show an intimate association between ColXV and fibrillar components in areas localized far from mineralized nodules.

CONCLUSIONS

We have demonstrated the efficacy of ultrastructural analysis, combined with immunocytochemistry, to establish a temporal and spatial localization of ColXV. This data, added to previous evidences, contribute to validate the negative effects of calcium deposits on ColXV expression.

Elevated extracellular calcium ions promote proliferation and migration of mesenchymal stem cells via increasing osteopontin expression

Supplementation of mesenchymal stem cells (MSCs) at sites of bone resorption is required for bone homeostasis because of the non-proliferation and short lifespan properties of the osteoblasts. Calcium ions (Ca2+) are released from the bone surfaces during osteoclast-mediated bone resorption. However, how elevated extracellular Ca2+ concentrations would alter MSCs behavior in the proximal sites of bone resorption is largely unknown. In this study, we investigated the effect of extracellular Ca2+ on MSCs phenotype depending on Ca2+ concentrations. We found that the elevated extracellular Ca2+ promoted cell proliferation and matrix mineralization of MSCs. In addition, MSCs induced the expression and secretion of osteopontin (OPN), which enhanced MSCs migration under the elevated extracellular Ca2+ conditions. We developed in vitro osteoclast-mediated bone resorption conditions using mouse calvaria bone slices and demonstrated Ca2+ is released from bone resorption surfaces. We also showed that the MSCs phenotype, including cell proliferation and migration, changed when the cells were treated with a bone resorption-conditioned medium. These findings suggest that the dynamic changes in Ca2+ concentrations in the microenvironments of bone remodeling surfaces modulate MSCs phenotype and thereby contribute to bone regeneration.

Biocompatibility and Osteogenic/Calcification Potential of Casein Phosphopeptide-amorphous Calcium Phosphate Fluoride

INTRODUCTION

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and CPP-ACP with fluoride (CPP-ACFP) have been shown to provide bioavailable ions to promote mineralization. Hence, the aim of this study was to evaluate the materials' biocompatibility and osteogenic/calcification potential for endodontic applications.

METHODS

Human and mouse osteoblast-like and fibroblast-like cell lines were incubated with 0.05%-3.0% w/v CPP-ACP and CPP-ACFP, and toxicity, proliferation, alkaline phosphatase, interleukin (IL)-1α, and IL-6 production, collagen type I, osteocalcin, and osteopontin production, and mineralization/calcification were determined.

RESULTS

CPP-ACP and CPP-ACFP were non-toxic and had no significant effect on proliferation or production of the inflammatory cytokine IL-1α. Alkaline phosphatase activity of the osteoblast-like cells was significantly increased (P < .05) by CPP-ACP and CPP-ACFP, as was the production of the osteotropic cytokine IL-6, the formation of calcium mineral deposits, and the secretion of mineralization-related proteins (collagen type I and osteocalcin).

CONCLUSIONS

CPP-ACP and CPP-ACFP are biocompatible and have the potential to induce osteoblastic differentiation and mineralization. Potential applications include apexification, perforation repair, vital pulp therapy, and regenerative endodontic procedures.

Collagen type XV and the 'osteogenic status'

We have previously demonstrated that collagen type XV (ColXV) is a novel bone extracellular matrix (ECM) protein. It is well known that the complex mixture of multiple components present in ECM can help both to maintain stemness or to promote differentiation of stromal cells following change in qualitative characteristics or concentrations. We investigated the possible correlation between ColXV expression and mineral matrix deposition by human mesenchymal stromal cells (hMSCs) with different osteogenic potential and by osteoblasts (hOBs) that are able to grow in culture medium with or without calcium. Analysing the osteogenic process, we have shown that ColXV basal levels are lower in cells less prone to osteo‐induction such as hMSCs from Wharton Jelly (hWJMSCs), compared to hMSCs that are prone to osteo‐induction such as those from the bone marrow (hBMMSCs). In the group of samples identified as ‘mineralized MSCs’, during successful osteogenic induction, ColXV protein continued to be detected at substantial levels until early stage of differentiation, but it significantly decreased and then disappeared at the end of culture when the matrix formed was completely calcified. The possibility to grow hOBs in culture medium without calcium corroborated the results obtained with hMSCs demonstrating that calcium deposits organized in a calcified matrix, and not calcium ‘per se’, negatively affected ColXV expression. As a whole, our data suggest that ColXV may participate in ECM organization in the early‐phases of the osteogenic process and that this is a prerequisite to promote the subsequent deposition of mineral matrix.

Regulation of CYP27B1 mRNA Expression in Primary Human Osteoblasts

The enzyme 1α-hydroxylase (gene CYP27B1) catalyzes the synthesis of 1,25(OH)2D in both renal and bone cells. While renal 1α-hydroxylase is tightly regulated by hormones and 1,25(OH)2D itself, the regulation of 1α-hydroxylase in bone cells is poorly understood. The aim of this study was to investigate in a primary human osteoblast culture whether parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), calcitonin, calcium, phosphate, or MEPE affect mRNA levels of CYP27B1. Our results show that primary human osteoblasts in the presence of high calcium concentrations increase their CYP27B1 mRNA levels by 1.3-fold. CYP27B1 mRNA levels were not affected by PTH1-34, rhFGF23, calcitonin, phosphate, and rhMEPE. Our results suggest that the regulation of bone 1α-hydroxylase is different from renal 1α-hydroxylase. High calcium concentrations in bone may result in an increased local synthesis of 1,25(OH)2D leading to an enhanced matrix mineralization. In this way, the local synthesis of 1,25(OH)2D may contribute to the stimulatory effect of calcium on matrix mineralization.

Recent advances in the understanding of molecular mechanisms of cartilage degeneration, synovitis and subchondral bone changes in osteoarthritis

Osteoarthritis (OA), the most common form of degenerative joint disease, is linked to high morbidity. It is predicted to be the single greatest cause of disability in the general population by 2030. The development of disease-modifying therapy for OA currently face great obstacle mainly because the onset and development of the disease involve complex molecular mechanisms. In this review, we will comprehensively summarize biological and pathological mechanisms of three key aspects: degeneration of articular cartilage, synovial immunopathogenesis, and changes in subchondral bone. For each tissue, we will focus on the molecular receptors, cytokines, peptidases, related cell, and signal pathways. Agents that specifically block mechanisms involved in synovial inflammation, degeneration of articular cartilage, and subchondral bone remodeling can potentially be exploited to produce targeted therapy for OA. Such new comprehensive agents will benefit affected patients and bring exciting new hope for the treatment of OA.

Milk-Derived Nanoparticle Fraction Promotes the Formation of Small Osteoclasts But Reduces Bone Resorption

The general consensus is that milk promotes bone growth and density because is a source of calcium and contains components that enhance intestinal calcium uptake or directly affect bone metabolism. In this study, we investigated the effect of bovine-derived milk 100,000 g pellet (P100), which contains nanoparticles (<220 nm) including extracellular vesicles, on osteoclast differentiation and bone resorption. Bone marrow-derived osteoclast precursor cells were differentiated into osteoclasts by M-CSF and RANKL (control) and in the presence of milk P100. Milk P100 treatment until day 4 increased the number of TRAP-positive mononuclear cells and small (≤5 nuclei) osteoclasts. The number of large (≥6 nuclei) osteoclasts remained the same. These alterations were associated with increased expression of TRAP, NFATc1, and c-Fos. Cells seeded in a calcium-phosphate coated plate or bone slices showed reduced resorption area when exposed to milk P100 during the differentiation phase and even after osteoclast formation. Interestingly, milk P100 treatment enhanced Cathepsin K expression but reduced Carbonic Anhydrase 2 gene expression. Moreover, intracellular acid production was also decreased by milk P100 treatment. Oral delivery of milk P100 to female DBA1/J mice for 7 weeks did not alter bone area; however, increased osteoclast number and area in tibia without changes in serum RANKL and CTX-I levels. We showed for the first time the effect of milk P100 on osteoclast differentiation both in vitro and in vivo and found that milk P100 increased the formation of small osteoclasts but this does not lead to more bone resorption probably due to reduced acid secretion. J. Cell. Physiol. 232: 225-233, 2017. © 2016 Wiley Periodicals, Inc.

Calcium sensing receptor activation by calcimimetic R-568 in human amniotic fluid mesenchymal stem cells: correlation with osteogenic differentiation

Human amniotic fluid mesenchymal stem cells (hAFMSCs) are promising for therapeutic applications in bone damage. Calcium sensing receptor (CaSR), a G protein-coupled receptor, plays a physiological role in the regulation of bone metabolism. Thus, the bone CaSR could be targeted by calcimimetic agonists, which may be potentially helpful in treating bone diseases. The aim of our study was to characterize CaSR expression in hAFMSCs and to assess the activity of calcimimetic R-568 during in vitro osteogenesis. Using western blotting, immunofluorescence, and flow cytometry, we consistently observed constitutive CaSR in osteo-differentiating hAFMSCs. Notably, both R-568 and calcium significantly enhanced hAFMSC osteogenic differentiation after exposure to osteogenic medium. To provide further evidence of the involvement of CaSR in osteogenesis, we correlated its expression with that of established osteogenic markers, that is, alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and osteopontin (OPN), and novel, not yet completely defined regulators of osteogenesis. Among these are β-catenin and Slug, which are mediators of Wnt signaling, and nuclear factor of activated T cells c1 (NFATc1), which plays a critical role in calcium/calcineurin signaling. Taken together, our results demonstrate that CaSR is expressed in hAFMSCs, positively correlates with osteogenic markers, and is activated by R-568. Notably, downregulation of CaSR by RNA interference supports the conclusion that CaSR activation plays a central role in hAFMSC osteogenesis. Thus, this study provides significant information on the mechanisms of hAFMSC osteogenesis, which could provide additional molecular basis for the use of calcimimetics in bone regenerative medicine.

Surface engineering of titanium alloy substrates with multilayered biomimetic hierarchical films to regulate the growth behaviors of osteoblasts

Osseointegration is essential for the long-term survival of orthopedic implants. Inspired by the hierarchical structure of natural bone, we fabricated a hierarchical structure with osteoinduction potential on titanium alloy (Ti6Al7Nb) substrates via a spin-assisted layer-by-layer assembly technique, with hydroxyapatite nanofibers as the intercalated materials and gelatin and chitosan as the polycation and polyanion, respectively. The as-synthesized hydroxyapatite nanofibers were characterized using scanning electron microscopy (SEM), transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The change of water contact angle corresponding to different layers indicated the formation of a multilayered structure, since different components have their inherent wettability natures. The multilayered lamellar structure was revealed by the cross-sectional view of SEM, suggesting that the film was successfully deposited onto Ti6Al7Nb substrates. Osteoblasts cultured on the hierarchical structure deposited Ti alloy substrates displayed significantly higher cell viability (P<0.01) and better adhesion, a higher production level of alkaline phosphatase, mineralization, genes expressions of osteocalcin and osteopontin (P<0.01 or P<0.05) compared to those of native Ti6Al7Nb substrates after culture for 4, 7 or 14days. These results indicated that the lamellar structure was beneficial for the biological functions of osteoblasts, establishing the basis for osseointegration of a titanium alloy implant.

Osteogenic and antimicrobial nanoparticulate calcium phosphate and poly-(D,L-lactide-co-glycolide) powders for the treatment of osteomyelitis

Development of a material for simultaneous sustained and localized delivery of antibiotics and induction of spontaneous regeneration of hard tissues affected by osteomyelitis stands for an important clinical need. In this work, a comparative analysis of the bacterial and osteoblastic cell response to two different nanoparticulate carriers of clindamycin, an antibiotic commonly prescribed in the treatment of bone infection, one composed of calcium phosphate and the other comprising poly-(D,L-lactide-co-glycolide)-coated calcium phosphate, was carried out. Three different non-cytotoxic phases of calcium phosphate, exhibiting dissolution and drug release profiles in the range of one week to two months to one year, respectively, were included in the analysis: monetite, amorphous calcium phosphate and hydroxyapatite. Spherical morphologies and narrow size distribution of both types of nanopowders were confirmed in transmission and scanning electron microscopic analyses. The antibiotic-containing powders exhibited sustained drug release contingent upon the degradation rate of the carrier. Assessment of the antibacterial performance of the antibiotic-encapsulated powders against Staphylococcus aureus, the most common pathogen isolated from infected bone, yielded satisfactory results both in broths and on blood agar plates for all the analyzed powders. In contrast, no cytotoxic behavior was detected upon the incubation of the antibiotic powders with the osteoblastic MC3T3-E1 cell line for up to three weeks. The cells were shown to engage in a close contact with the antibiotic-containing particles, irrespective of their internal or surface phase composition, polymeric or mineral. At the same time, both types of particles upregulated the expression of osteogenic markers osteocalcin, osteopontin, Runx2 and protocollagen type I, suggesting their ability to promote osteogenesis and enhance remineralization of the infected site in addition to eliminating the bacterial source of infection.

T cell subsets differently regulate osteogenic differentiation of human mesenchymal stromal cells in vitro

T lymphocytes play a key role in the regulation of bone homeostasis and bone healing. The inflammatory response at the site of bone injury is essential to the initiation of the bone repair program; however, an uncontrolled exposure to inflammatory environment has a negative effect on tissue regeneration - indeed, activated T cells were shown to inhibit osteogenic differentiation on human mesenchymal stromal cells (MSCs). Whether resting T cells can induce osteogenic differentiation of MSCs and what role specific T cells subset play in this process is still elusive. In this study, we sought to analyse the osteogenic gene expression profile of whole T cells, CD4 and CD8 T cells isolated from healthy donors and investigated whether secreted factors from each group modulate osteogenic differentiation of human MSCs. Gene expression profiling identified a pool of 51 genes involved at various stages in bone growth which are expressed above detectable levels in CD4 and CD8 T cells. Most genes of this pool were expressed at higher levels in the CD4 subset. In vitro mineralization assays revealed that conditioned medium from CD4 T cells, but not from CD8 cells, significantly increased mineralization in osteogenic cultures of human MSCs; furthermore, mRNA expression of Runt-related transcription factor 2 (RUNX-2), osteocalcin (OC), bone sialoprotein (BSP) and alkaline phosphatase (ALP) in MSCs was significantly upregulated in the presence of CD4-conditioned medium but not with that obtained from CD8. The results show a differential role for CD4 and CD8 T cells in supporting bone formation and identify an osteogenic gene signature of each subset.

Effect of low-level laser therapy on odontoblast-like cells exposed to bleaching agent

The aim of the present study was to evaluate the effect of low-level laser therapy (LLLT) on odontoblast-like MDPC-23 cells exposed to carbamide peroxide (CP 0.01%-2.21 μg/mL of H2O2). The cells were seeded in sterile 24-well plates for 72 h. Eight groups were established according to the exposure or not to the bleaching agents and the laser energy doses tested (0, 4, 10, and 15 J/cm(2)). After exposing the cells to 0.01% CP for 1 h, this bleaching solution was replaced by fresh culture medium. The cells were then irradiated (three sections) with a near-infrared diode laser (InGaAsP-780 ± 3 nm, 40 mW), with intervals of 24 h. The 0.01% CP solution caused statistically significant reductions in cell metabolism and alkaline phosphate (ALP) activity when compared with those of the groups not exposed to the bleaching agent. The LLLT did not modulate cell metabolism; however, the dose of 4 J/cm(2) increased the ALP activity. It was concluded that 0.01% CP reduces the MDPC-23 cell metabolism and ALP activity. The LLLT in the parameters tested did not influence the cell metabolism of the cultured cells; nevertheless, the laser dose of 4 J/cm(2) increases the ALP activity in groups both with and without exposure to the bleaching agent.